Non-Adherence to medications is a common problem in clinical practice especially among patients with asymptomatic chronic conditions like type II diabetes and hypercholesterolemia in whom some 50% of patients are non-adherent. The costs of poor adherence to medications have been estimated to approach $100 billion dollars a year and are the result of adverse outcomes such as hospitalization, the development of complications, disease progression, premature disability or death. Non-Adherence is the result of a complex interaction among the social environment, the patient and the health providers. Adherence to medications is not routinely measured in clinical practice and a gold standard that can be easily implemented even for research purposes does not exist. Yet, the use of claims data to measure adherence has been shown useful and, given the relatively small costs associated with its use, its implementation in routine clinical practice appears both feasible and sustainable. However, more information is needed on the validity of the method and on the consequences of making adherence information available to both patients and physicians. Using The Chronic Care model as a theoretical framework, we propose a two-phase study. In Phase I, claims data will be used to identify diabetic patients receiving pharmacological treatment for both diabetes and hypercholesterolemia and to measure their A to medications prescribed for the two conditions. The association between adherence indices and intermediate outcomes (glycosylated hemoglobin and cholesterol levels) will be estimated. In Phase II, qualitative (focus groups) and quantitative methods (telephone and mail surveys) will be used to examine patients' attitudes, beliefs, barriers, relationship with providers, and stages of change towards adherence and towards the introduction of adherence information in clinical practice in conjunction with the Health Belief and Stages of Change Models as explanatory theories. The study will help clarify the association between adherence and clinical outcomes as well as to estimate the predictive and convergent validity of prescription claims data as a method of measuring adherence to medications. Finally, we will explore intrinsic factors at the patient level related to adherence, and patient and provider preferences and attitudes towards the use of adherence information in routine clinical practice. [unreadable] [unreadable]